1. Field of the Invention
The present invention relates to a current sensor that detects a current to be measured, which flows through a current path, by detecting a magnetic field generated by the current to be measured.
2. Description of the Related Art
In recent years, a sensor using a magnetoresistive element (a GMR element or a TMR element) having a laminated structure of a fixed magnetic layer whose magnetization direction is fixed, a nonmagnetic layer, and a free magnetic layer whose magnetization direction is changed with respect to the external magnetic field has been suggested. For example, in the field of motor driving technology in electric vehicles or hybrid cars, a relatively large current is handled. Accordingly, a current sensor capable of measuring a large current in a non-contact manner has been demanded for these applications.
As such a current sensor, there is a current sensor that detects a change in the magnetic field, which is generated by the current to be measured, using a magnetic detection element.
In a current sensor disclosed in U.S. Pat. No. 8,994,365, magnetic detection units are disposed on the top and bottom surfaces of a substrate, and the sensitivity is adjusted such that the outputs of the two magnetic detection units match each other to determine the presence or absence of a failure.
In the known current sensor described above, however, an S/N ratio that is a ratio between the strength of a magnetic field generated by the current to be measured, which flows through the current path, and the strength of an external magnetic field is different between the two magnetic detection units. Accordingly, if the external magnetic field is large, failure may be determined even though there is no failure in practice since the external magnetic field is different even if the magnetic field generated by the current to be measured at the positions of the two magnetic detection units is the same. In particular, in a case where the magnetic field from the current to be measured is small, erroneous failure determination increases.
In addition, in the current sensor described above, there is a demand for miniaturization.